The present description relates generally to the field of propulsion systems for manually-operated mobility devices, such as manual wheelchairs, recumbent bicycles, and other manually-propelled mobility devices. More specifically, the present description relates to a propulsion system including a planetary gear system for propelling a manually-operated mobility device.
It is well known to provide mobility devices such as wheelchairs that are manually propelled by persons having certain physical injuries, disabilities or ailments. According to one estimate, there are approximately 1.8 million manual wheelchair users in the United States and the population is expected to grow at a rate of 10% annually. Studies have shown that long-term manual wheelchair users may be 50% more likely to suffer upper extremity muscle overuse. The effects of muscle overuse becoming evident in the forms of muscle pain, torn rotor cuffs, joint degeneration, and carpal tunnel syndrome. Studies have found that the continued prevalence and intensity of pain, over time, resulted in a change in lifestyle where the user ceased to routinely perform these activities. It would be desirable to minimize these types of injuries while retaining the benefits of the exercise that these devices and other manually operated mobility devices provide.